In Time of Flight (“TOF”) mass spectrometry a mixture of species of differing masses is accelerated into a mass analyser and the ions are separated according to their mass to charge ratio. Enough time is allowed for the largest mass to charge ratio species of ion present in the mixture to reach an ion detector before a next or subsequent acceleration event is initiated, in a so-called “pulse-and-wait” approach. This technique has an inherently low duty cycle and sensitivity, especially when used with continuous ion sources. For instance, in the case of an orthogonal acceleration folded flight path (“FFP”) Time of Flight analyser waiting for this length of time leads to very low duty cycles (e.g. 0.3% or less).
It is known that the low duty cycle can be mitigated to some extent by sampling more often than that determined by the flight time of the largest mass to charge ratio species of ion and then demultiplexing the resulting spectral data in a process which is known as “oversampling”.
However, one problem with this approach is that when the oversampling approach is utilised with rich and complex spectra (such as is often found in liquid chromatography mass spectrometry experiments) then the resulting data can include too many peak overlaps for successful demultiplexing.
With current low duty cycle (0.3% or less) folded flight path analysers it is desired to be able to oversample by a factor of approximately 100 in order to achieve substantially improved duty cycles of ˜30%.
Accordingly, it is desired to provide an improved method of mass spectrometry.